Discovery of the hidden coding information in cancers: Mechanisms and biological functions.

Most proteins are derived from the translation of coding sequence (CDS) in messenger RNAs (mRNAs). However, accumulating evidence has revealed an unexpected abundance of translation in putative non-coding genomes, especially 5' untranslated region (5' UTR) of mRNAs or non-coding RNA species (ncRNA) such as long non-coding RNAs (lncRNAs) and circular RNAs (circRNAs). Notably, many of these UTR- or ncRNA-encoded micropeptides/proteins play important roles in human malignancies. In this review, we describe recent advances in our understanding of the mechanisms underlying the translation of non-coding regions or ncRNAs and the methods to discover the hidden coding information. Furthermore, we summarize the biological functions of UTR- or ncRNA-encoded micropeptides/proteins in cancers and discuss their potential as clinical biomarkers for cancer diagnosis and as therapeutic targets for cancer treatment.